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Lecture

Astronomy – Session 5

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Department
Astronomy
Course
ASTA02H3
Professor
Parandis Khavari
Semester
Winter

Description
Astronomy – Session 5  HR Diagram  luminosity (L) versus temperature (T) plot  two factors: size and temperature  learn how to plot a HR Diagram  note that temperature increases from right to left  terminology  white dwarves  main sequence  super giants  giants  white dwarves  very hot  very small  very dense  almost as heavy as the Sun  mass  of the Sun  ex. Sirius B  main sequence stars  make up a majority of the stars seen in the sky  source of energy for 90% of the stars (on the graph)  burn Hydrogen into Helium  majority of a stars life is spent in main sequence  longest period of a star’s life  young  red dwarves  small luminosity and radii  bottom right of the area main sequence stars occupy  super giants and giants  large stars  huge radii  brown dwarves  not stars  spectral class  eight main categories of stars  O, B, A, F, G, K, M, N  each divided by a subclass  ranges from zero to nine  problem  does not provide numerical descriptions  luminosity-mass relationship  only applies to main sequence stars  L ∝ R T 2 4  correlates with the spectral class  O, B, A, F, G, K, M, N 2  R 4efers to the size or the radius of a star  T refers to the surface temperature of a star  luminosity-mass relationship equation variation      if     HR Diagram  stars on a vertical line  keeping temperature constant  the hotter a star is, the brighter it is  radius increases as you go up the dotted line  increase in radius when mov
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